release/src/router/libvorbis/lib/lookup.c

   1 /********************************************************************
   2  *                                                                  *
   3  * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
   4  * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
   5  * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
   6  * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
   7  *                                                                  *
   8  * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2009             *
   9  * by the Xiph.Org Foundation http://www.xiph.org/                  *
  10  *                                                                  *
  11  ********************************************************************
  12
  13   function: lookup based functions
  14   last mod: $Id: lookup.c 16227 2009-07-08 06:58:46Z xiphmont $
  15
  16  ********************************************************************/
  17
  18 #include <math.h>
  19 #include "lookup.h"
  20 #include "lookup_data.h"
  21 #include "os.h"
  22 #include "misc.h"
  23
  24 #ifdef FLOAT_LOOKUP
  25
  26 /* interpolated lookup based cos function, domain 0 to PI only */
  27 float vorbis_coslook(float a){
  28   double d=a*(.31830989*(float)COS_LOOKUP_SZ);
  29   int i=vorbis_ftoi(d-.5);
  30
  31   return COS_LOOKUP[i]+ (d-i)*(COS_LOOKUP[i+1]-COS_LOOKUP[i]);
  32 }
  33
  34 /* interpolated 1./sqrt(p) where .5 <= p < 1. */
  35 float vorbis_invsqlook(float a){
  36   double d=a*(2.f*(float)INVSQ_LOOKUP_SZ)-(float)INVSQ_LOOKUP_SZ;
  37   int i=vorbis_ftoi(d-.5f);
  38   return INVSQ_LOOKUP[i]+ (d-i)*(INVSQ_LOOKUP[i+1]-INVSQ_LOOKUP[i]);
  39 }
  40
  41 /* interpolated 1./sqrt(p) where .5 <= p < 1. */
  42 float vorbis_invsq2explook(int a){
  43   return INVSQ2EXP_LOOKUP[a-INVSQ2EXP_LOOKUP_MIN];
  44 }
  45
  46 #include <stdio.h>
  47 /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
  48 float vorbis_fromdBlook(float a){
  49   int i=vorbis_ftoi(a*((float)(-(1<<FROMdB2_SHIFT)))-.5f);
  50   return (i<0)?1.f:
  51     ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
  52      FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
  53 }
  54
  55 #endif
  56
  57 #ifdef INT_LOOKUP
  58 /* interpolated 1./sqrt(p) where .5 <= a < 1. (.100000... to .111111...) in
  59    16.16 format
  60
  61    returns in m.8 format */
  62 long vorbis_invsqlook_i(long a,long e){
  63   long i=(a&0x7fff)>>(INVSQ_LOOKUP_I_SHIFT-1);
  64   long d=(a&INVSQ_LOOKUP_I_MASK)<<(16-INVSQ_LOOKUP_I_SHIFT); /*  0.16 */
  65   long val=INVSQ_LOOKUP_I[i]-                                /*  1.16 */
  66     (((INVSQ_LOOKUP_I[i]-INVSQ_LOOKUP_I[i+1])*               /*  0.16 */
  67       d)>>16);                                               /* result 1.16 */
  68
  69   e+=32;
  70   if(e&1)val=(val*5792)>>13; /* multiply val by 1/sqrt(2) */
  71   e=(e>>1)-8;
  72
  73   return(val>>e);
  74 }
  75
  76 /* interpolated lookup based fromdB function, domain -140dB to 0dB only */
  77 /* a is in n.12 format */
  78 float vorbis_fromdBlook_i(long a){
  79   int i=(-a)>>(12-FROMdB2_SHIFT);
  80   return (i<0)?1.f:
  81     ((i>=(FROMdB_LOOKUP_SZ<<FROMdB_SHIFT))?0.f:
  82      FROMdB_LOOKUP[i>>FROMdB_SHIFT]*FROMdB2_LOOKUP[i&FROMdB2_MASK]);
  83 }
  84
  85 /* interpolated lookup based cos function, domain 0 to PI only */
  86 /* a is in 0.16 format, where 0==0, 2^^16-1==PI, return 0.14 */
  87 long vorbis_coslook_i(long a){
  88   int i=a>>COS_LOOKUP_I_SHIFT;
  89   int d=a&COS_LOOKUP_I_MASK;
  90   return COS_LOOKUP_I[i]- ((d*(COS_LOOKUP_I[i]-COS_LOOKUP_I[i+1]))>>
  91                            COS_LOOKUP_I_SHIFT);
  92 }
  93
  94 #endif